Counter for condensation nuclei in air

ABSTRACT

The condensation chamber of a recording counter for small airborne dust particles is first flushed with the air to be tested by drawing the air through inlet and discharge valves by a suction pump, the chamber is sealed, and its contents are saturated with moisture while being compressed isothermally in a ratio of 1:1.18 to 1.25. Upon subsequent adiabatic decompression through a suddenly opened valve of relatively large flow section, water droplets form on the nuclei provided by dust particles and are photographed so that they may be counted on the developed film. The apparatus is operated automatically in cycles at chosen intervals.

United States Patent 91 Kanter [4 Nov. 26, 1974 COUNTER FOR CONDENSATIONNUCLEI 27, No. 5, May 1956, pp. 273-7.

IN AIR Junge et al., Journal of Meteorol gy, Vol. 18, No. 1, [75]Inventor: Hans Joachim Kanter, February, 1961, pp. 81-108.

Garmisch-Partenkirchen, Germany [73] Assignee: Max-Planck-Gesellschaftzur Primary Examiner-Ronald L. Wibert Forderund der Wissenschaften e.v.,Assistant ExaminerR. J. Webster Gottingen, Germany Attorney, Agent, orFirmHans Berman 22 Filed: Mar. 16, 1973 v 1 pp 341,989 [57 ABSTRACT Thecondensation chamber of a recording counter for [30] Foreign ApphcatlonPnomy Data small air-borne dust particles is first flushed with the Mar.24. 1972 Germany 2214463 air to be tested by drawing the air throughinlet and discharge valves by a suction pump, the chamber is [52]- U-S.Cl 356/3 25 3, 356/103 sealed, and its contents are saturated withmoisture [51] Int. Cl. ..G0lm1/00,G0lm 21/00. while being compressedisothermally in a ratio of [58] Field of Search 356/37, 103, 107, 108;1:1.18 to 1.25. Upon subsequent adiabatic decompres- 8, 573-577 sionthrough a suddenly opened valve of relatively large flow section, waterdroplets form on the nuclei [56] References Cited provided by dustparticles and are photographed so UNITED STATES PATENTS that they may becounted onthe developed film. The 3.756.720 9/1973 Skala 356/37apparatus is Operated automatically in cycles at OTHER PUBLICATIONSSaunders, The Review of Scientific Instruments, Vol.

chosen intervals.

10 Claims, 7 Drawing Figures PROGRAMMING mm WQ' AL lfi 53 51. 3 1F 57 5355 l l 1 r L g PUWER numn MUTUR V SUPPLY MElIHM STARTER 13 17 36 a -1.7%,, that. W 151 7 1a 22 Ll] VALVE 55 2 CONTROLLER 21 cLncK 55 l SHEET10F 4 EE 2 e :3. a W $258 3 a Z 5%; as: v 5 m3 E: 22:22:

PATEHTL T'T'ivzs m4 Fig.6

SHEET a or 4 sucnuu VALVE (m DECUMPRESSIUN 17 VALVE 1 FLASH TUBE CAMERAFLASH TUBE MIRRUR WATER VALVE cmnRuLT PISTON 5 MUTUR STARTER (5B) 4 mmVALVE (m T T T T T T T EH 9 LE EL-..

compression seconds t COUNTER FOR CONDENSATION NUCLEI IN AIR Thisinvention relates to a counter for condensation nuclei in air, andparticularly to a modification of the nuclei counter of John Aitkenwhich permits automatic and periodic determination of submicroscopiccondensation nuclei in air.

In a known modification of Aitkens original counter (J. of Meteorology18 [1961] 81-108), a normally closed receiver is provided with a pistonor plunger arranged for movement into and out of the receiver and forthereby changing the effective capacity of the receiver cavity, an inletvalve for admitting air to the receiver, a discharge valve for releasingthe air, and a water supply system for saturating the air in thereceiver with moisture. A camera is focused on a plane in the receivercavity, and its field may be illuminated instantaneously by a flash oflight to produce a photographic image. The nuclei are visible on thephotographic record as images of spherical condensation droplets, andthe diameters of the images increase by lack of sharpness with theirdistance from the plane of sharp delination toward or away from theobjective lens system of the camera. The relationship between the sizeof the circles of confusion representing the droplets and the distanceof the nuclei from the plane of sharp delineation is determined bycalculation or by experimental calibration.

It has been proposed to operate the known apparatus automatically, butthe known automatic operating arrangements have been found to be complexand correspondingly costly when reliable, and unsatisfactory in theirreliability and precision if simple in their construction.

The primary object of the invention is the provision of an automaticallyoperated nuclei counter satisfying requirements for high precision whilebeing of sufficiently simple construction to operate reliably overextended periods of time without being attended.

The improved counter arrangement of the invention has a receiveradditionally provided with a decompression valve leading directly intothe ambient atmosphere for expansion of a tested air sample previouslycompressed in the receiver, a receptacle in the receiver communicatingwith a water supply line controlled by a valve in response to the waterlevel in the receptacle, and with a programming mechanism whichenergizes the electrically operated parts of the counter arrangement ina timed cycle. The inlet and discharge valves are opened first and thepiston or plunger is withdrawn from the receiver cavity for flushing thelatter with ambient air drawn through the valves by suction, and thewater level control device is energized. Thereafter the inlet anddischarge valves are closed, thepiston or plunger is moved inward of thereceiver for compressing the air sample, whereafter the decompressionvalve is opened for sudden expansion of the air sample, and ultimatelythe flash illuminator is energized while the camera shutter is open toproduce a latent image on the photosensitive film or other material inthe camera. The operating cycle is terminated by closing thedecompression valve, and the apparatus is ready for the next cycle.

The submicroscopic condensation nuclei which are of interest arerecorded selectively when the ratio of the effective capacities of thereceiver capacity in the two terminal positions of the plunger or pistonis between 1:l.18 and 111.25.

The nuclei are uniformly distributed in the receiver, and particularlyin the portion of the receiver accessible for recording, when thereceiver cavity has a cylindrical shape, and is bounded axially by thepiston or plunger at one axial end and by an observation window for thecamera at the other end, and when the orifices of the inlet anddischarge valves are located in the receiver wall at diagonally oppositepoints of a plane parallel to the cavity axis.

It is not normally required to count condensation nuclei at intervals asshort as the duration of one operating cycle, and the programmingmechanism preferably includes an interval timer which starts respectiveoperating cycles at intervals longer than one operating cycle andcapable of being adjusted.

For reasons not yet fully explored, the photographic records obtained intests repeated under identical conditions are most precisely reproducedif the piston or plunger moves inward of .the receiver during itscompression stroke at a constant speed.

The apparatus of the invention has been found emi- 4 nently suitable forrecording condensation nuclei having each a radius of 10' to 10 cm andbeing present in the atmosphere at a concentration of 200 to 600 nucleiper cubic centimeter. Such conditions are characteristic of pure airover the ocean or over the continents at altitudes above 3,000 meters.Because of its operating characteristics, the apparatus is well suitedfor unmanned exploration of the atmosphere. It is accurate enough toprovide a reference standard for less sophisticated nuclei counters.

Other features, additional objects, and many of the attendant advantagesof this invention will readily become apparent from thefollowingdetailed description of a preferred embodiment when consideredin connection with the appended drawing in which:

FIG. 1 shows a counter arrangement of the invention in elevationalsection, electrical and optical devices being represented in aconventional manner;

FIG. 2 shows a portion of the arrangement of FIG. 1 on a larger scaleand in greater detail in section on the line II-II in FIG. 3;

FIG. 3 shows a portion of the device of FIG. 2 in plan section;

FIG. 4 illustrates a part of the device of FIG. 3 on a further enlargedscale;

FIG. 5 diagrammatically illustrates the image recording process in thecounter;

FIG. 6 is a timing diagram of the programming unit in the apparatus ofFIG. 1; and

FIG. 7 shows an auxiliary device for use with the apparatus of FIG. 1 ina conventional manner.

Referring now to the drawing in detail, and initially to FIG. 1, thereare seen a condensation chamber assembly l, a photographic recordingunit 2, and a programming mechanism 3 which constitute the principalelements of the counter arrangement.

The condensation chamber assembly 1 includes a receiver 4 having acylindrical cavity bounded in one axial direction by a piston 5 so thatthe effective capacity of the cavity may be decreased or increased bymovement of the piston 5 into and out of the receiver 4. In theillustrated terminal position of the piston 5, the cavity capacity is atits maximum.

The piston may be pushed inward of the receptacle 4 and into its other,non-illustrated terminal position by a radial cam 7 which engages a camfollower roller 8 on the piston rod 6. A helical compression springholds the cam follower 8 in engagement with the cam 7. The cam 7 ispivoted back and forth by a reversing gear motor 64 after the startercontrols 58 for the motor 64 are energized by a programming unit 53 inthe mechanism 3 which also includes an interval timer 54.

Three solenoid valves communicate with the cavity of the receiver 4, andare operated by the programming unit 53. A two-way inlet valve 13normally directs air drawn from the ambient atmosphere through a by-passconduit 15 to a suction pump 16 equipped with a builtin electric motorso that the valve 13 is swept free of deposited dust particles. When thesolenoid of the valve 13 is energized by the programming unit 53, thevalve 13 admits air from the atmosphere to the receiver 4. A normallyclosed discharge or suction valve 14, when operated by the unit 53,connects the receiver 4 directly to the suction pump 16. A normallyclosed decompression valve 17 having a flow section much greater thanthat of the valves 13, 14 permits the receiver cavity to be brought intodirect communication with the ambient atmosphere for quick release ofsuperatmospheric pressure.

Air in the receiver 4 may be saturated with moisture from a receptacle18 in which the water level is sensed by a detector 22 connected to acontroller 56 for a normally closed, solenoid-operated water valve 21.When the controller 56 is activated by the unit 53, and the detector 22senses a water level below a set level in the receptacle 18, the valve21 is opened to admit water from a water line, not shown in detail, tothe receptacle 18, and the valve 21 closes the water line when thedesired level is reached in the receptacle 18.

A portion of the cavity in the receiver 4 may be illuminated by means ofa circular, electronic flashtube 26, and the illuminated cavity portionmay be photographed by means of a camera 36 when a mirror 41 is tiltedout of the field of the camera 36 by an electromagnetic tiltingmechanism 63 controlled by the unit 53 in parallel circuit with thedecompression valve 17 and with the power supply 57 of the flash tube 26which includes a time delay circuit.

In the illustrated position, the mirror 41 reflects into the camera 36an image of the dial on a clock 45 when the clock is illuminated by anelectronic flash tube 65 whose non-illustrated power supply is connectedto a flash terminal on the camera 36 in a manner not specifically shown,the camera being operated electrically from time to time by theprogramming unit 53. The film transport mechanism, not itselfillustrated, in the camera 36 is electrically operated and provided withan emergency shut-off unit 51 connected to a temperature sensor 52. Ifthe film jams the transport mechanism, the temperature in the motor ofthe latter rises, and the temperature increase is sensed by the sensor52 which causes the shut-off unit 51 to open the energizing circuit ofthe electric motor in the film transport mechamsm.

As is better seen in FIGS. 2 and 3, a 120 portion of the cam face on theradial cam 7 spirals away from the axis of cam rotation in such a mannerthat the piston 5 is moved inward of the receiver 4 at a uniform linearspeed when the shaft 7' of the cam 7 is moved at uniform angularvelocity by the gear motor 64. The portions of the cam face merging witheither end of the spiralling portion are circular about the axis of theshaft 7', and the piston stands still in its terminal positions whilethe cam follower 8 travels over the circular cam face portions duringacceleration and deceleration of the motor 64. Two limit switches,obscured by the cam 7, are operated by an abutment on the shaft 7' inthe terminal piston positions. When the piston 5 reaches the illustratedposition, one limit switch reverses the motor 64 and opens a holdingcircuit in the starter 58, so as to stop the motor, and the other limitswitch reverses the motor 64 in the non-illustrated piston position ofminimum cavity volume.

For the convenience of manufacture, the receiver 4 consists of threeflangedly connected, axial parts 12, 11, 1 l' which are coaxial,cylindrical tubes of the same diameter. The part 12 is closed by aradial end wall 9 in which the piston rod.6 is slidably sealed. Anelongated, wide slot 19 in the bottom of the central receiver part 11 isclosed in a radially outward direction by a shallow trough 20 welded tothe outer face of the receiver 4 so that the slot 19 and the trough 20jointly bound a receptacle 18, the valve 21 communicating with thebottom of the trough 20.

The flanges 29 which axially connect the receiver parts 11, 11' inaxially spaced relationship provide an annular chamber in which theflash tube 26 is mounted. The chamber is sealed from the receiver cavityby a short, cylindrical glass tube 27 flush with the inner walls of thereceiver parts 1 l, l 1'. The inner wall of the receiver part 11 islined with a non-illustrated, black velvet which dips into thereceptacle 18 and acts as a wick for humidifying air in the receiver.Openings in the velvet expose the orifice 13' of the valve 13 and themuch greater orifice 17 of the valve 17.

The axial end of the receiver part 11' remote from the piston 5 issealed by a radial glass plate 23 held in position by an annular cap 24.The light reaching the glass plate 23 from the flash tube 26 is limitedto those rays which are deflected in a portion of the receiver cavityindicated by the broken line 25 by a stop arrangement 28 consisting ofthree centrally apertured plates 31, 32, 33 axially interposed betweenthe cavity portion 25 and the glass plate 23.

The lens barrel 34 of the camera 36 is sealed into the central openingof the cap 24 and encloses the objective lens system 35 of the camera.The rear end of the barrel 34 is fixedly attached to one tubular part 38of rigid bellows 37, the other tubular part 39 telescoping in the part38 in light-tight engagement and being attached to the body 36' of thecamera 36 for exposure of film 43 in the camera body which is that of aconventional, electrically operated 16 mm movie camera equipped forsingle-frame exposure by electric remote control, and for film advanceafter each exposure. The camera body, which may be a staple article ofcommerce, has not been illustrated in detail. It may be shifted towardand away from the barrel 34 in a conventional manner, not shown.

A side tube 44 projecting from the bellows tube 39 at right angles tothe optical axis of the objective lens system 35, which coincides withthe axis of the receiver 4, encloses another objective lens 42 andcarries at its far end the electric clock 45 indicating the date, hour,

and minute on its non-illustrated dial. The afore-' described tiltablemirror 41 is arranged in the bellows 37 for either reflecting an imageof the illuminated dial on the clock 45 or for permitting the recordingof events in the cavity portion 25.

As is shown in even greater detail in FIG. 4, beveled annular edges 30of the receiver parts 11, 11' project toward each other so as further toshield the camera 36 from stray light of the flash tube 26. Lightreaching the glass plate 23 and transmitted thereby to the camera islimited to a circular area of diameter 46 in the center of the plate 23,and such light is deflected by particles in the cavity portion 25.

As is diagrammatically illustrated in FIG. 5, the objective lens system35 is focussed on a plane 49, and a condensed water droplet formed on aspeck of dust as a nucleus during decompression of the receiver cavityappears sharp on the film 43 after the latter is developed. The imagesof droplets in front or behind the plane 49 are larger, as is indicatedby light rays represented by fully drawn and broken lines respectively.The diameter D of a circle 50 indicating a condensed droplet in planes47, 48 located at a selected known distance from the plane 49 is readilycalculated from the known parameters of the optical system. The numberof nuclei in a volume of air axially bounded by the planes 47, 48 andradially bounded by a cylinder whose diameter may be derived from thediameter 46 is determined by counting on the developed film 43 all spotswhose diameter is equal to or smaller than D. This volume of airoccupies the portion 25 of the receiver cavity, so that this portionconstitutes an optically defined test cell within the cavity. The testcell is located in the center of the area illuminated by the tube 26.

The manner in which a typical nuclei counter arrangement of theinvention is automatically operated by the programming unit 53 isevident from the timing schedule of FIG. 6 which assumes an operatingcycle of 60 seconds. The unit 53 may consist of a rotary, multiple-deckswitch driven by a gear motor which is energized by the timer 54 forturning the rotary switch through one revolution, and by associatedrelays, as is conventional in itself.

At the time t =0, the piston 5 is in the non-illustrated positionnearest the camera 36. When the motor of the programming unit 53 isstarted, and its relays are connected to a battery or the like, by theinterval timer 54, the solenoids of the valves l3, 14 are energized toopen the valve 14 and to connect the receiver cavity to the atmospherethrough the valve 13, and the pump 16 is energized so that a stream ofthe ambient air to be tested is drawn through the receiver 4. Afterseconds from the start of the cycle, the motor 64 is started by itscontrol 58, and the cam 7 starts turning toward the illustratedposition, thereby permitting the spring 10 to withdraw the piston 5towards the position shown in the drawing and thereby to increase thereceiver capacity by a factor of 1.21:1. Shortly before the terminalposition of the piston 5 is reached, at t sec., the water valvecontroller 56 is energized and opens the valve 21 to bring the water inthe receptacle 18 to its prescribed level. If the water level were notset at this stage, the air volume in the receiver 4 after completewithdrawal of the piston 5 would not be precisely defined. The dischargevalve 14 is closed at t 28 sec., and the valve controller 56 issimultaneously deenergized. Because the pump 16 maintained slightlysubatmospheric pressure in the receiver 4 while the valve 14 was open,the valve 13 is closed only at t sec., when the air, in the receiver hasreached atmospheric pressure.

Simultaneously, the piston 5 starts moving inward of the receiver 4under the action of the cam 7 to compress the air sealed in the receivercavity. The piston moves at uniform linear speed for 20 seconds duringits compression stroke. The piston movement is slow enough and the heatcapacity of thereceiver 4 suffi cient to keep the air temperatureconstant during compression. The sealed body of air is being saturatedwith moisture from the receptacle 18. At t 55 sec., the programming unit53 opens the non-illustrated shutter of the camera 36, and the flashtube 65 is simultaneously energized by way of the synchronizing contactof the camera so as to illuminate the dial of the clock 45.

At t 55.5 sec., the programming unit 53 closes the energizing circuitsof the mirror tilting mechanism 63, of the decompression valve 17, andof the power supply 57 for the flash tube 26. The mirror 41 is tiltedout of the optical axis of the objective lens system 35, and the wideopening of the valve .17 causes sudden, and practically adiabatic,expansion of the air in the receiver 4. The air temperature drops, andthe air becomes supersaturated with water. The submicroscopic nucleiaccumulate respective, visible droplets of water.

Because of the delay circuit in the power source 57, the flash bulb 26is energized only 0.4 seconds after the opening of the decompressionvalve, and the latent image of the droplets within the field of theobjective lens system 35 is superimposed on the previously formed imageof the clock 45. The film 43 is advanced in the camera body 36' by oneframe.

At t 59 sec., the solenoid of the valve 17 is deenergized, and the valveis closed by its return spring. Simultaneously, the'mirror tiltingmechanism 63 is deen-v ergized, letting the mirror 41 return to itsstarting position by gravity. The camera also is deenergized to closethe shutter and thereby to advance the film 43 by one frame. At t 60sec., the starting condition of the apparatus is restored, and theprogramming unit is ready to begin another cycle upon a signal from theinterval timer 54, the latter being a rotary timing switch continuouslyoperated at low speed.

In the counter arrangement whose operation has been described above withreference to FIG. 6, the axial boundaries of the portion 25 of thereceiver cavity may be'selected for a testcell volume of about 0.15 to0.3 cm. The objective lens system 35 is achromatic and has a resolutionpower of approximately 300 lines per millimeter, approximately equal tothe resolution power of the photosensitive emulsion on the film 43. Theglass of the window 23 absorbs all light of wavelengths for which theobjective lens system 35 is not fully corrected, particularlyultraviolet radiation.

The apparatus described so far is capable of furnishing a readilyevaluated photographic record of condensation nuclei up to aconcentration of 2,000 per cubic centimeter. It is preferred, however,to dilute the tested air when the concentration of nuclei exceeds 1,200per cm". A suitable diluting attachment 59 for the inlet valve 13 isshown in FIG. 7. It consists essentially of a dustfilter 61 and athrottle valve 62 connected to a mixing vessel 60, the intake ends ofthe filter 61 and the valve 62 being open to the ambient atmosphere, andthe mixing vessel 60 being connected to the valve 13.

The suction of the pump 16 draws air into the mixing vessel 60 in eitherposition of the valve 13 through the filter 61 and the valve 62 so thatthe ambient air entering through the valve 62 is diluted with airsubstantially completely stripped of nuclei by the filter 61. It ispreferred to set the valve 62 for the same pressure drop under normaloperation conditions as occurs in the filter 61.

When equipped with the diluting attachment of FIG. 7, the useful rangeof the counter arrangement is expanded substantially beyond 2,000 nucleiper cm. The lower useful counting limit is at aproximatly 20 nuclei percm and far below the range of 200 to 600 condensation nuclei to beexpected in pure air.

The structural features of the counting arrangement and the mode ofoperation described above by way of example permit selective counting ofcondensation nuclei having diameters between 10 to 4 10' cm which are ofspecial interest to meteorologists. Nuclei constituted by small ionshaving radii smaller than 8 X 10 are not recorded, nor is the recordfalsified by larger particles. At the preferred compression or expansionratio between 1: 1.18 and 121.25, only condensed droplets not producedby homogeneous condensation of water molecules are detected. As has beenshown above, the counter arrangement of the invention permits operationunder conditions in which the droplets cannot fall by gravity from thetest cell 25 at the moment at which the photographic record is produced,and while they are still distributed in the test cell at random.

Such a distribution is initially produced by the fact that the orificesof the valves 13,14 in the receiver cavity are located in axially spacedportions of a plane parallel to the cavity axis, and are oppositelyspaced from the axis, that is, diagonally spaced from each other in therectangular plane. As is evident from FIG. 3, the plane preferablyincludes the cavity axis, and such an arrangement has been found toimprove reproducibility of test results.

It should be understood, of course, that the foregoing disclosurerelates only to a preferred embodiment of the invention, and that it isintended to cover all changes and modifications in the example of theinvention herein chosen for the purpose of the disclosure which do notconstitute departures from the spirit and scope of the invention setforth in the appended claims.

What is claimed is:

l. A counter arrangement for counting condensation nuclei in ambient aircomprising, in combination:

a. a receiver bounding a cavity therein;

b. inlet valve means operable for admitting said air to said cavity whensaid valve means is open;

c. suction means for withdrawing admitted air from said cavity;.

(1. decompression valve means operable to be opened for directlyconnecting said cavity to said ambient air;

e. a piston member movable into and outward of said receiver between twoterminal positions for decreasing and increasing the efi'ective capacityof said cavity;

f. saturating means for saturating said air in said cavity withmoisture, said saturating means including a receptacle, and levelcontrol means operable for maintaining in said receptacle a constantlevel of water exposed to said cavity;

g. a camera focused on a portion of said cavity;

h. illuminating means operable for illuminating said portion of saidcavity; and

i. programming means for cyclically operating said inlet valve means,said suction means, said decompression valve means, said piston member,said saturating means, and said illuminating means in timed sequence. 0

2. An arrangement as set forth in claim 1, wherein the effective flowsection of said decompression valve means is substantially greater thanthe effective flow section of said inlet valve means.

3. An arrangement as set forth in claim 2, wherein said effectivecapacity of said cavity in said one terminal position of said pistonmember is 1.18 to 1.25 times the effective capacity of said cavity insaid other terminal position of said piston member.

4. An arrangement as set forth in claim 2, wherein said cavity has anaxis and is cylindrical about said axis, said cavity being bounded inone axial direction by said piston member, said receiver including awindow bounding said cavity in the other axial direction, said camerabeing focussed on said portion through said window, said inlet valvemeans and said suction means communicating with said cavity throughrespective orifices in said receiver located in a common plane parallelto saidaxis and oppositely offset from said axis in respective portionsof said plane axially spaced from each other.

5. An arrangement as set forth in claim 2, further comprising intervaltiming means operatively connected to said programming means forstarting respective cycles of operation thereof at predeterminedintervals.

6. An arrangement as set forth in claim 2, further comprising drivemeans operated in response to said programming means and operativelyconnected to said piston member for moving the same between saidterminal positions thereof at uniform linear speed.

7. An arrangement as set forth in claim 2, further comprising stop meanspreventing light of said illuminating means from by-passing said portionof the cavity and directly entering said camera.

8. An arrangement as set forth in claim 2, further comprising a sourceof visible indicia, light deflecting means movable between two positionsfor alternatively directing light from said portion of said cavity andfrom said source to said camera, said programming means including meansfor moving said light deflecting means in timed sequence with saidilluminating means for thereby deflecting light from said portion tosaid camera while said illuminating means are energized while deflectinglight from said source to said camera when said illuminating means arenot energized.

9. An arrangement as set forth in claim 2, further comprising dilutingmeans for diluting said ambient air with a gas substantially free fromsaid nuclei prior to the admitting of said air to said cavity by saidinlet valve means.

10. An arrangement as set forth in claim 1, wherein said programmingmeans include 1. means for opening said inlet valve means and actuatingsaid suction means for flushing said cavity with said air,

2. means for moving said piston member after said opening of said inletvalve means outward of said receiver into one of said terminalpositions, and for actuating said level control means,

3. means for deactivating said suction means and member,

closlng Sald f valve means after 531d outward 6. means for energizingsaid illuminating means after movmg of the Piston m m said opening ofsaid decompression valve means, 4. means for moving said piston memberinward of and said receiver into the other terminal position after Saidclosing of Said inlet valve means, 7. means for closing saiddecompression valve means 5. means for opening said decompression valveafter Said energizingmeans after said inward moving of said pistonUNETED STATES PATENT OFFICE I CERTIFLCATE @E CGRREQTWN Patent No. '8Dated November w 1-974 iinventms) ms JOACHIM KAWER It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

In the heading, line {737, change Mam-Plenck sesellsehaft 2m:

Farrier-and. der Wissenschaften ecv. to

' Max Plenck-G esellsahaft zur Forderunq der Wissenschaften e.V.

Signed and sealed this 18th day of February 1975.

(SEAL) Attest: Ca MARSHALL DANN RUTH C. MASON I Commissioner of PatentsAttesting Officer and Trademarks USCOMM-DC 60376-1 69 e vs. GOVERNMENTPRINTING OFFICE 1959 o-ase-ssa.

| FORM F'O-IOSO (10-69)

1. A counter arrangement for counting condensation nuclei in ambient aircomprising, in combination: a. a receiver bounding a cavity therein; b.inlet valve means operable for admitting said air to said cavity whensaid valve means is open; c. suction means for withdrawing admitted airfrom said cavity; d. decompression valve means operable to be opened fordirectly connecting said cavity to said ambient air; e. a piston membermovable into and outward of said receiver between two terminal positionsfor decreasing and increasing the effective capacity of said cavity; f.saturating means for saturating said air in said cavity with moisture,said saturating means including a receptacle, and level control meansoperable for maintaining in said receptacle a constant level of waterexposed to said cavity; g. a camera focused on a portion of said cavity;h. illuminating means operable for illuminating said portion of saidcavity; and i. programming means for cyclically operating said inletvalve means, said suction means, said decompression valve means, saidpiston member, said saturating means, and said illuminating means intimed sequence.
 2. means for moving said piston member after saidopening of said inlet valve means outward of said receiver into one ofsaid terminal positions, and for actuating said level control means, 2.An arrangement as set forth in claim 1, wherein the effective flowsection of said decompression valve means is substantially greater thanthe effective flow section of said inlet valve means.
 3. An arrangementas set forth in claim 2, wherein said effective capacity of said cavityin said one terminal position of said piston member is 1.18 to 1.25times the effective capacity of said cavity in said other terminalposition of said piston member.
 3. means for deactivating said suctionmeans and closing said inlet valve means after said outward moving ofthe piston member,
 4. means for moving said piston member inward of saidreceiver into the other terminal position after said closing of saidinlet valve means,
 4. An arrangement as set forth in claim 2, whereinsaid cavity has an axis and is cylindrical about said axis, said cavitybeing bounded in one axial direction by said piston member, saidreceiver including a window bounding said cavity in the other axialdirection, said camera being focussed on said portion through saidwindow, said inlet valve means and said suction means communicating withsaid cavity through respective orifices in said receiver located in acommon plane parallel to said axis and oppositely offset from said axisin respective portions of said plane axially spaced from each other. 5.An arrangement as set forth in claim 2, further comprising intervaltiming means operatively connected to said programming means forstarting respective cycles of operation thereof at predeterminedintervals.
 5. means for opening said decompression valve means aftersaid inward moving of said piston member,
 6. means for energizing saidilluminating means after said opening of said decompression valve means,and
 6. An arrangement as set forth in claim 2, further comprising drivemeans operated in response to said programming means and operativelyconnected to said piston member for moving the same between saidterminal positions thereof at uniform linear speed.
 7. An arrangement asset forth in claim 2, further comprising stop means preventing light ofsaid illuminating means from by-passing said portion of the cavity anddirectly entering said camera.
 7. means for closing said decompressionvalve means after said energizing.
 8. An arrangement as set forth inclaim 2, further comprising a source of visible indicia, lightdeflecting means movable between two positions for alternativelydirecting light from said portion of said cavity aNd from said source tosaid camera, said programming means including means for moving saidlight deflecting means in timed sequence with said illuminating meansfor thereby deflecting light from said portion to said camera while saidilluminating means are energized while deflecting light from said sourceto said camera when said illuminating means are not energized.
 9. Anarrangement as set forth in claim 2, further comprising diluting meansfor diluting said ambient air with a gas substantially free from saidnuclei prior to the admitting of said air to said cavity by said inletvalve means.
 10. An arrangement as set forth in claim 1, wherein saidprogramming means include